on-print

Arguments:
dialog-item

Returns the value of the on-print event property of
dialog-item.
The value of the on-print property should be a
function object or a function name (a symbol naming a function), or
nil. nil means use
princ-to-string.

The function which is the value of this property is called whenever
the dialog-item's value is being formatted for
display in the dialog-item. It is also called for each member of the
dialog-item's range when the range is a list of
possible values that are shown in the control. The function should
accept one argument, which is the value itself, and should return a
string to display in the dialog-item for that value. The default
differs for various dialog-item classes, but is usually a standard
print function such as princ-to-string.

Using an on-print
function allows the value of a dialog-item to be a meaningful Lisp
object while the visible control itself displays an arbitrary
nicely-formatted string to represent it. This is particularly useful
in controls that display a set of choices: when the user selects a
value, there is no need to map from the selected string to a
meaningful lisp object, since that lisp object will be the control's
value.

Most dialog-items that can display strings implement on-print. In addition, a list-view-column
object may be given an on-print function to format the
values in a single column of a list-view control differently than
other columns of the same control. And a combo-box-column-mixin grid-column
may be a given an on-print function to format the
values in its drop-down list of choices (though the value displayed in
the actual cell is formatted by the column's data-read-converter).

See cg-events.htm for information about
event handling in Common Graphics.

Copyright (c) 1998-2012, Franz Inc. Oakland, CA., USA. All rights reserved.Documentation for Allegro CL version 9.0. This page was not revised from the 8.2 page.Created 2012.5.30.